<!DOCTYPE html>
<html>
<head>
    <meta charset='UTF-8'>
    <title>直接在HTML中输出流</title>
</head>
<body>
    <h1>你好</h1>
    <script>
        document.write("<h1>我是JavaScript</h1>");
    </script>
    <h1>我去</h1>
    <button onclick="over()" type="">千万别按</button>
</body>
<script>
    function over(){
        document.write("<h1>啥都没了</h1>");
    }
</script>
</html>